Field
Embodiments of the disclosure relate generally to the field of propulsion systems for aircraft and more particularly to a single blade propeller with variable pitch employing an electrically powered pitch control mechanism as a counterweight.
Background
Solar powered airplanes are typically powered by electrical motors receiving power from a solar array on the surface of the aircraft and driving multiple bladed propellers. In most cases these airplanes are designed for very high altitude flight with long duration flight profiles. Performance of such solar powered airplanes is very sensitive to component efficiency. Propeller efficiency is approximately equivalent in importance to airframe lift to drag (L/D). In example prior art systems a 2.0% absolute efficiency improvement in propeller efficiency may offset an airplane weight increase of 1.3% or increase winter solstice maximum latitude by approximately 1°.
Additionally, such solar powered airplanes have little reserve power for climb, even at low altitude. In dense low altitude air at slow flight speeds, the motor bogs down at low propeller rotational speed (RPM). Even though the airplane requires far less power to fly, the motor is current-limited by overheating concerns and produces little excess power.
It is therefore desirable to provide a means to increase motor RPM to increase motor power without exceeding the current limit.